1. Field of the Invention.
This invention relates in general to antenna systems, and in particular to a slot coupled patch reflect array element for enhanced gain-bandwidth performance.
2. Description of Related Art.
Communications satellites have become commonplace for use in many types of communications services, e.g., data transfer, voice communications, television spot beam coverage, and other data transfer applications. As such, satellites must provide signals to various geographic locations on the Earth""s surface. As such, typical satellites use customized antenna designs to provide signal coverage for a particular country or geographic area.
Typical antenna systems use either parabolic reflectors or shaped reflectors to provide a specific beam coverage, or use a flat reflector system with an array of reflective printed patches or dipoles on the flat surface. These xe2x80x9creflect arrayxe2x80x9d reflectors used in antennas are designed such that the reflective patches or dipoles shape the beam much like a shaped reflector or parabolic reflector would, but are much easier to manufacture and package on the spacecraft.
The conventional elements used in a typical reflect array antenna are printed dipoles or printed patches. Reflect arrays using such elements are typically design limited to have either a narrow bandwidth or a low gain. The gain and bandwidth of a reflect array antenna system is dependent upon the electrical characteristics of the elements. For a patch element (or dipole element) the phase versus length curve, typically known as the xe2x80x9cS-curvexe2x80x9d because the shape of the curve looks like an inverted xe2x80x9cS,xe2x80x9d is very stiff, i.e., the slope of the curve is very steep through the phase change region. Further, the phase variation is not linear with frequency. Therefore the reflect array elements used in such an antenna system cannot maintain the desired phase distribution over a wide frequency range. The stiffness of the S-curve can be improved by using a thicker substrate for the patch or dipole elements of the reflect array. However, the thicker substrate elements have a reduced dynamic range of the phase of each element. As a result, some of the patch or dipole element phases that are beyond the available dynamic range cannot be realized by varying the physical dimensions of the patch elements. This causes a reduction in the gain of the element array antenna system, and prevents a high gain, wide band performance from a reflect array using conventional patch or dipole elements.
It can be seen, then, that there is a need in the art for reflect array elements that have a high dynamic range of the phase for each element. It can also be seen that there is a need in the art for reflect array elements that have a high gain while maintaining a high dynamic range of the phase for each element.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses an antenna element, an antenna system, and a method for producing a signal using slot-coupled antenna elements. The antenna element comprises an electrically conductive strip, a patch element, overlaying the electrically conductive strip, and a ground plane. The ground plane is coupled between the patch element and the electrically conductive strip and comprises an opening, at least a portion of the opening overlapping with at least a portion of the electrically conductive strip, wherein the opening and the electrically conductive strip can reflect incident radio frequency (RF) energy in a desired radiation pattern.
A method in accordance with the present invention comprises illuminating a reflector with an RF signal emanating from a feed horn, wherein the reflector comprises at least one reflect array antenna element, and reflecting the RF signal from the reflect array element, wherein the reflect array element comprises an electrically conductive strip, a patch element, overlaying the electrically conductive strip, and a ground plane. The ground plane is coupled between the patch element and the electrically conductive strip and comprises an opening, at least a portion of the opening overlapping with at least a portion of the electrically conductive strip, wherein the opening and the electrically conductive strip assist in generating the desired radiation pattern
The present invention provides reflect array elements that have a high dynamic range of the phase for each element. The present invention also provides reflect array elements that have a high gain while maintaining a high dynamic range of the phase for each element.